Water-repellent ultramarine



Patented July 6, 1943 WATER-REPELLENT ULTRAMARINE Henry Frederick Dieterle, Cedar Grove, N. 1., assignor to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Original application September 4,

1940, Serial No. 355,313. Divided and this application June 16, 1942, Serial No. 447,276

17 Claims.

This invention relates to a water repellent ultramarine.

' There is a considerable demand for a water repellent ultramarine particularly for such purposes as the blueing of coal for trade-marking purposes. Ordinarily an ultramarine when applied to coal or other surfaces can be caused to gather principally in the cracks of the solid substrate from a water suspension. However, the coloring thus produced is not permanent because it washes off when the coal is exposed to the weather and particularly to the rain, and similar problems are presented with other applications of ultramarine from water suspensions to insoluble substrates.

It has been tried in the past to incorporate ultramarine with rosin size and then to precipitate an insoluble resinate such as an aluminum resinate. This product has been applied to the blueing of coal and similar problems but without great success; adhesion is insufiicient and the product still washes off. This problem therefore may be considered as one of combined adhesion and water repellency.

The difficulties encountered with the resinate suspensions which have been used before may be due to a number of factors. Without intending to limit the present invention to any particular theory of action, I believe that at least one factor is the characteristic of the film or coating of insoluble resinate which is produced, and it is my belief that this film is not sufficiently sticky and oieaginous so as to cause good adherence. Probably another factor is that the film itself does not show a suficient affinity for the surface of the coal to produce good adhesion. Probably there are other factors also involved.

According to the present invention, ultramarine is coated with a film of insoluble higher fatty acid. The higher fatty acids which are used in the present invention and which form insoluble coatings include the usual higher fatty acids, but I find that the best results are obtained with oleic acid or coconut oil acids and similar lower molecular fatty acids which are insoluble. While, therefore, useful products may be produced with the other fatty acids, I prefer to use oleic acid.

Since the purpose of this invention is to produce a suspension of ultramarine coated and associated with the insoluble higher fatty acid compounds, any suitable method of producing this coating may be used. Thus, for example, a suspension of ultramarine in a solution of a soluble higher fatty acid compound such as soluble alkali metal soaps may be prepared and then insoluble fatty acid precipitated by an acid.

Since the ultramarine produced by the present invention is highly water repellent and for that reason not readily dispersible in water, it is frequently' desirable to incorporate in the suspension of the pigment in water, a soluble wetting or dispersing agent so as'to facilitate thorough dispersion and ready adherence. I have found that the most satisfactory dispersing agents are of the diethyleneglycol mono-ether type. The mono-butyl ether of diethyleneglycol is particu-, larly useful. The dispersing agent may be incorporated into the suspension at any stage of its manufacture. Best results are, however, obtained when the wetting agent is incorporated with the soluble soap solution before precipitation of the insoluble fatty acid onto the ultramarine. The finest and most uniform coating and best adherence appears to be produced when the dispersing agent is introduced at this stage, and this constitutes the preferred method of introduction, although the invention is not limited thereto.

Since the most important large commercial use for the water repellent ultramarine of the present invention is in the blueing of anthracite coal for trade-mark purposes, the. invention will be described in greater detail in conjunction with the production of suspensions of water repellent ultramarine suitable for application to the coal. The effectiveness of the coating and its water repellency are tested by coating anthracite coal in the standard manner and then subjecting it to washing for an hour under a shower of water.

While the product of the present invention is used on a large scale in the blueing of coal, and this is its most important commercial use at the present time, the process of blueing coal and the product obtained are not claimed in this case, but form the subject matter of my copending application Serial No. 426,289, filed January 10, 1942.

The invention will be described in detail in connection with the following specific example, the parts being by weight.

. Example 14 oz. of caustic soda are added to 8 lbs. of cold water and 1.6 lbs. of mono-butyl ether of diethyleneglycol are added. The solution is heated to -60 C. by blowing insteam and then 6 lbs. of oleic acid are added. The mixture is agitated and heated to the boil and held there with continued agitation until the solution is quite clear and a sample dissolves in water completely leaving no oil film. This requires about one hour. After the clear solution is obtained, 2.4 lbs. of mono-butyl ether of diethyleneglycol are added and heating is continued for about fifteen minutes. The amount of water present at this time including the condensed steam should be about lbs. The solution is then cooled to 40-60 C. 1,000 lbs. of ultramarine, preferably very finely ground, are put in a vessel such as a dough mixer. The mixing mechanism is started and while the ultramarine is turned over, sodium oleate solution is slowly and very uniformly added to it. After all of the oleate has been added, the material is finally passed through a hammer mill in order to obtain a very complete distribution of the solution over the ultramarine.

The water repellent ultramarine produced can be used in blueing coal by dispersing it in water to form a. homogeneous slurry, for example, 100 lbs. of ultramarine may be dispersed in about 10,000 lbs. of water. To this dispersion there is then added sufiicient sulfuric acid to neutralize all of the alkali present and to precipitate free oleic acid. The suspension can then be sprayed onto coal in the usual manner and after drying forms an adherent deposit mainly in the depressions of the coal which is not washed out to any appreciable extent when the coal is immersed in water or exposed to a shower of water. The ultramarine particles are coated with a water repellent'film of oleic acid which has good adherence and which, after drying, does not redisperse in water. The coating is absent or light on the fiat surfaces of the coal, and concentrated in the depressions.

The properties of the product of the example are determined by examining the shade after spraying the coal, then washing for an hour under a shower of fresh water, and examining the shade after such washing, the examinations being both in the wet state and under artificial light. The characteristics are compared with a blueing effected by following the procedure of the above example, but using 4 lbs. of aluminum sulfate per 100 lbs. of ultramarine instead of the sulfuric acid. This latter product is used at present on a large scale in the blueing of anthracite coal and will be referred to as the type, the shades of the product of the example being compared to it in the following table:

' Visibility Before washing Shade After washing Visibility wet Similar to Better than Better than Similar to type. type. type. type.

The extraordinary difference between. the product of the present invention and that obtainable in the past using resinates presents a complex problem because the individual ultramarine particles when examined under the microscope do not permit accurate determination of the differences, as the film is translucent or transparent and is hence not readily visible. The result of the present invention is all the more surprising because ordinary water repellent pigments including prior water repellent ultramarine cannot be dispersed in water. They clump together to form nonhomogeneous suspensions and therefore cannot be used in the form of water suspensions. The dispersing agent such as the ether of diethyleneglycol is needed to impart a temporary dispersibiiity to the coated ultramarine. However, if this dispersibility were permanent, the product would wash right off. Such, however, is not the case of the examples in the table above. This temporary dispersibility which disappears on coating the coal may be due to a number of factors and it is not desiredtoi limit the present invention to any particular theory. I believe, however, that at least one factor and perhaps the most important factor is due to a removal of the dispersing agent in solution in the water in which the ultramarine is suspended and quite probably also be evaporation as the coating dries. Possibly other factors are involved as chemical changes may take place during the drying of the coating. I believe, however, that the permanent water repellency of the dried coating is primarily due to physical removal of the dispersing agent and this is advanced as the most probable explanation or the surprising change which takes place in the nature of the ultramarine when its suspension is applied to a surface and dried.

In the example, oleic acid has been described as the higher fatty acid. The acids of coconut oil give equally good results. Pure acid is not necessary, technical grades being useful, and similar results are obtained with other acids such as palmitic and stearic although the film in the case of oleic and coconut acids shows somewhat better adherence. Other alkyl ethers of diethyleneglycol may be used as dispersing agents such as the mono-ethyl ether and other water-soluble dispersing agents may be used such as for example alkali metal salts of higher alkyl sulfuric acids, salts of alkyl naphthalene sulfonic acids, salts of esters of sulfosuccinic acid, and the like. Best results are however, obtained with the mono-alkyl ethers of diethyleneglycol which are therefore the preferred dispersing agents.

The nature of the acid used in transforming the film of soap into a film of free fatty acid is not critical, as the anion of the acid does not form any part of the film, but unites with the alkali metal of the soap and is removed by the excess water spray. Therefore for practical operations, the cost of the acid is the main consideration and for this reason sulfuric acid, which is the cheapest acid available, is preferred for practical commercial operation.

This application is a division of my copending application Serial No. 355,313, filed September 4, 1940.

What I claim is:

l. A method of producing a water dispersion of ultramarine capable of drying on a surface to a water repellent non-dispersible ultramarine coating which comprises homogeneously coating finely ground ultramarine with a very thin film of a soluble soap of a higher fatty acid by admixing a solution of said soap with ultramarine until homogeneous coating results and suspending the coated ultramarine in water in the presence of a water soluble dispersing agent and in the presence of suflicient acid to react with the soap and transform the film 'into a film of free fatty acid.

2. A method of producing a water dispersion of ultramarine capable of drying on a surface to a water repellent non-dispersible ultramarine coating which comprises homogeneously coating finely ground ultramarine by admixing therewith a small amount of a water solution of a soluble soap of a higher fatty acid and a water soluble volatile wetting agent while kneading the ultramarine, continuing the kneading until a homogeneous coating of the ultramarine is effected, and suspending the coated ultramarine in water containing sufficient acid to react with the soap and to transform the latter into a film of free fatty acid.

3. A method of producing a water dispersion of ultramarine capable of drying on a surface to a water repellent non-dispersible ultramarine coating which comprises homogeneously coating finely ground ultramarine with a very thin film of an alkali metal L leate by admixing a solution of said alkali metal oleate with ultramarine until homogeneous coating results and suspending the coated ultramarine in water in the presence of a water soluble dispersing agent and in the presence of sufficient acid to react with the alkali metal oleate and transform the film into a film of free fatty acid.

4. A method of producing a water dispersion of ultramarine capable of drying on a surface to a water repellent non-dispersible ultramarine coating which comprises homogeneously coating finely ground ultramarine by admixing therewith a small amount of a water solution of an alkali metal oleate and a water soluble volatile wetting agent while kneading the ultramarine, continuing the kneading until a homogeneous coating of the ultramarine is eiiected, and suspending the coated ultramarine in water containing suflicient acid to react with the alkali metal oleate and to transform the latter into a film of free fatty acid.

5. A method according to claim 1 in which the acid used to react with the soap is sulfuric acid.

6. A method according to claim 2 in which the acid used to react with the soap is sulfuric acid.

7. A method according to claim 3 in which the acid used to react with the soap is sulfuric acid.

8. A method according to claim 4 in which the acid used to react with the soap is sulfuric acid.

9. An aqueous suspension of ultramarine coated with a thin film of a water insoluble higher fatty acid associated with a water soluble volatile wetting agent, said dispersion being capable of drying to produce a coating of Water repellent ultramarine which is not redispersible in water.

10. An aqueous suspension of ultramarine coated with a thin film of oleic acid associated with a water soluble volatile wetting agent, said dispersion bein capable of drying to produce a coating of water repellent ultramarine which is not redispersible in water.

11. An aqueous suspension of ultramarine coated with a thin film of the acid of coconut oil associated with a water soluble volatile wetting agent, said dispersion being capable of drying to produce a coating of water repellent ultramarine which is not redispersible in water.

12. A product according to claim 9 in which the wetting agent is a mono-alkyl ether of diethyleneglycol.

13. A product according to claim 10 in which the wetting agent is a mono-alkyl ether of diethyleneglycol.

14. A product according to claim 11 in which the wetting agent is a mono-alkyl ether of diethyleneglycol.

15. A product according to claim 9 in which the dispersing agent is monobutyl ether of diethyleneglycol.

16. A product according to claim 10 in which the dispersing agent is monobutyl ether of diethyleneglycol.

17. A product according to claim 11 in which the dispersing agent is monobutyl ether of diethyleneglycol.

HENRY FREDERICK DIETERLE. 

